1. Field of the Invention
The present invention relates to apparatus for sensing oil in an internal combustion engine, and more particularly to such sensors that detect the level of oil in a reservoir of the engine and that provide a signal indicating the viscosity of the oil.
2. Description of the Related Art
Internal combustion engines are lubricated by oil that is stored in a reservoir, typically an oil pan located underneath the cylinder block of the engine. An oil pump draws the oil from the reservoir and forces it through passages to the top of the cylinder block. After exiting those passages, the oil lubricates various components of the engine, as it flows downward through the cylinder block by gravity ultimately returning into the reservoir.
A sensor often has been used to detect pressure at the outlet of the oil pump to provide an indication to the operator of the engine whether there is sufficient oil for proper lubrication. However, this pressure sensor does not provide an indication of the oil's viscosity. Engine lubricating oil is commercially available in different viscosities and a particular engine is designed to use a specific type of oil. If oil of an improper viscosity for a given engine is used, the components of that engine may not be properly lubricated and damage to those components may result.
Therefore, it is desirable to determine whether there is a sufficient amount of oil within the reservoir and whether that oil is the proper viscosity.
Operation of an engine usually is controlled by a microcomputer that monitors the level of engine usage and the operating conditions. From such monitoring the microcomputer is able to determine when the lubricating capability of the oil becomes depleted and the oil needs to be replaced. At that time the microcomputer provides an indication of that need to the engine operator. When the oil is changed, the service technician must manually reset that indication, a process that differs for each make of motor vehicle. Therefore, it is desirable to provide a mechanism by which the microcomputer can detect when the oil has been changed and automatically reset the oil change indication.